Off-shell structures of nucleon-nucleontmatrices and their influence on nucleon-nucleus elastic scattering observables

The sensitivity of nucleon-nucleus elastic scattering observables to the off-shell structure of nucleon-nucleon t matrices, derived from realistic NN potentials, is investigated within the context of a full-folding model based on the impulse approximation. Our study uses recently developed NN potential models, which describe a subset of the NN data base with a χ² per datum ~1, which means that the NN t matrices are essentially on-shell equivalent. We calculate proton-nucleus elastic scattering observables for ¹⁶O, ⁴⁰Ca, and ²⁰⁸Pb between 100 and 200 MeV laboratory energy. We find that the elastic scattering observables are insensitive to off-shell differences of the employed NN t matrices. A more detailed investigation of the scattering equation and the optical potential as given in a factorized approximation reveals that the elastic scattering observables do not sample the NN t matrices very far off-shell where they exhibit differences.